The incubation of bacterial cultures is a standard laboratory technique in numerous biological studies. Monitoring the growth of these cultures in a shaker bath or fermentor currently requires frequent manual sampling. The work on this project has been aimed at developing a system capable of continuously monitoring growth in situ using optical measurements techniques. To date the work has demonstrated the feasibility of making these measurements in shaker flasks employing an immersed detection system and yeilded a prototype system for this application. Additional efforts have been directed at designing a system which will operate in a commercial type fermenter. The principal problem of eliminating gas bubbles in the optical path of the immersed probe has been solved.